Fan



H. A. KNOX June 5, 1934.

FAN

Filed April 7, 1932 Inventor Harr Alinux Patented June 5, 1934 UNITEDSTATES PATENT OFFICE 1 Claim.

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described hereinmay be manufactured and used by or for the Government for governmentalpurposes, without the payment to me of any royalty thereon.

This invention relates to a fan.

The principal object of the invention is to provide a fan whose velocitywill be automatically varied inversely to the speed of the motor drivingthe fan.

A further object is to provide an arrangement of the vanes which willinsure equal loading over the entire area of the vane.

To these and other ends, the invention consists in the construction,arrangement and com- 16 bination of elements described hereinafter andpointed out in the claim forming a part of this specification.

'A practical embodiment of the invention is illustrated in theaccompanying drawing, wherein:

Fig. 1 is a View in front elevation of a fan constructed in accordancewith the invention.

Fig. 2 is a longitudinal sectional view through a portion of the fan.

Fig. 3 is a view in side elevation of one of the vanes and indicating indotted lines the deflected position at high speed.

The fan is of the Sirocco type comprising a hub 6, which in thepresent-instance is the driven flywheel of an engine, and oblong vanes'7 arranged annularly about the hub and supported in spaced relationthereto with their trailing portions on a baiile plate 8 and with theirleading portions on a ring 9 carried by. spokes 10. The bafiie plate 8and spokes 10 are secured respectively to the margin and theperiphery ofthe hub 6 by means of bolts 8a and 10a.

The baflle plate 8 is inclined with respect to the hub 6 and itsperiphery is on a shorter radius than the periphery of the ring 9 sothat the vanes supported by these members are inclined relative to theaxis of rotation of the fan. By virtue of this arrangement the leadingportion of the vane being required to travel through a greater circlelocity than the trailing portion for a purpose in the same unit of timewill have a higher ve'- .apertures in the vanes and each having its endssecured in a turnbuckle 15.

The vanes '7 are flexible and are capable of being deflected to positionindicated in dotted lines in Fig. 3, when the fan is being driven at therate of 2,000 R. P. M. The flexibility of the blades is determined on abasis of initial deflection at 500 R. P. M. As the deflection variesbetween these velocities the area of the vane will automatically vary,being decreased as the velocity increases. This provision effects aconsiderable saving in motive power.

The flexibility of the vanes is preferably obtained by forming them of aplurality of leaves of varying height. In the present instance fourleaves are employed, designated a, b, c, and d, secured at their base bymeans of rivets 16. The leaf d is essentially a reinforcing strip andmay be of thicker metal without flexibility to facilitate mounting ofthe vane in the slots 11 and 12. 7

As shown in Fig. 2 a shroud 1'7 terminates adjacent the leading edge ofthe vanes.

In operation the air passing through the fan tends to pile up againstthe baffle plate 8 so that where the vanes are disposed parallel to theaxis of rotation there is an unequal loading or distribution and thetrailing portion of the vanes performs most of the work. By incliningthe vanes as proposed herein and giving the leading portion a highervelocity the pressures and loading are equally distributed over theentire area of the vanes. By thus eliminating the inefi'ective portionsof the vane it is possible to reduce their size. This arrangement isalso of particular advantage in connection with the use of flexiblevanes as it prevents distortion of the vanes.

I claim:

A fan including a hub, a bailie plate secured in an inclined position onthe periphery of the hub, spokes on the periphery of the hub and spacedfrom the baiiie plate, a ring carried by the spokes, said ring andbafiie plate formed with a plurality of slots, an annular series offlexible vanes mounted in the slots of the ring and baflie plates, lugson the vanes engageable with the sides of the ring and bafiie plate, anda cable passing through all of the vanes and holding them in place.

HARRY A. KNOX,

